Crystal Oscillator Information | What are the factors that affect the stability of quartz crystal oscillators?

Crystal oscillator is also a crystal oscillator. Crystal oscillator has many applications in life, such as CPU clock. Not all friends know something about crystal oscillators, so in this article, we will introduce the frequency stability of crystal oscillators and analyze the factors that affect the frequency stability of quartz crystal oscillators.

Frequency stability is a measure of how an oscillator's output frequency may change due to temperature changes during operation. If the frequency drifts beyond the application's expectations, timing errors may occur. Frequency stability is expressed in parts per million, or ppm, relative to a nominal frequency over a specific temperature range.

One of the main characteristics of quartz crystal oscillators is stability within the operating temperature , which is an important factor in determining the price of crystal oscillators. The higher the stability or the wider the temperature range, the higher the price of the device. The range of -40~+85℃ stipulated by industrial standards is often just out of the designers' habits. If -20~+70℃ is enough, then there is no need to pursue a wider temperature range. Design engineers must carefully determine the actual needs of a specific application and then specify the stability of the crystal oscillator. Too high a specification means more money.

The aging of quartz crystal oscillator is another important factor causing frequency changes. Depending on the life expectancy of the target product, there are various ways to mitigate this effect. Crystal aging will cause the output frequency to change according to a logarithmic curve, which means that this phenomenon is most significant in the first year of product use. For example, a crystal that has been used for more than 10 years will age about three times as fast as in the first year. This situation can be improved by using special crystal processing technology, or it can be solved by adjustment. For example, voltage can be applied to the control pin (that is, adding a voltage control function), etc.

Other factors related to stability include supply voltage, load changes, phase noise and jitter , and these active crystal oscillator specifications should be specified. For industrial products, it is sometimes necessary to put forward vibration and impact indicators. Military supplies and aerospace equipment often have more requirements, such as tolerances when pressure changes, tolerances when exposed to radiation, etc.

The material used to make quartz crystal oscillators is generally artificial quartz crystal, which allows large-scale production and reduces costs. Only a small number of people use natural quartz crystals. However, the number of imported crystal oscillator materials is increasing, and many crystal oscillator manufacturers In order to save costs, inferior materials are used to produce crystal oscillators in large quantities. Using such raw materials can easily lead to problems such as low accuracy of chip crystal oscillators or cylindrical crystal oscillators, insufficient temperature, failure to vibrate, and malfunctions.

When selecting devices, some margin should generally be left to ensure product reliability. Choosing higher-end devices can further reduce the probability of failure and bring potential benefits. This should also be considered when comparing product prices. In order for the "overall performance" of the quartz crystal oscillator to be balanced and reasonable, it is necessary to weigh many factors such as stability, operating temperature range, crystal aging effect, phase noise, cost, etc. The cost here not only includes the price of the device, but also Includes the lifetime cost of the product.